Bob Marshall was on the phone in his office at Johns Hopkins Bayview Medical Center in East Baltimore when he heard the boom, felt the building shake and saw the plume of smoke on the horizon.

"This is what we've trained for," he thought.

As news poured in that a train had derailed and caused a large explosion less than two miles away in Rosedale, Marshall, the hospital's emergency services administrator, began rapidly putting together an incident command center to deal with a potential influx of casualties.

At MedStar Franklin Square Medical Center, about four miles north of the derailment site, medical staff treated two men who suffered cuts and bruises when the building they were in partly collapsed and a female first responder whose ears were damaged, hospital officials said.

Capt. Bruce Schultz, a Baltimore County Fire Department spokesman, said one person hit by a falling ceiling fan was taken to a local hospital, and a Maryland Transportation Authority officer was assessed by medical staff at the scene of the explosion.

Marshall said Bayview staff saw just one patient, who wrongly thought she might have been exposed to toxic fumes.

Officials determined after gaining access to train manifests that the explosion posed no danger of contamination to the public. But in the initial hour after the explosion, people weren't sure, Marshall said. And they weren't about to take any chances.

After the explosion, Marshall handed out walkie-talkies to staff members, gathered stretchers and made sure operating rooms were available in the hospital's burn center. Chaplains and trauma therapists were put on call.

Marshall and other hospital officials discussed altering the hospital's ventilation system to isolate certain sections for contaminated patients and pitching large tents outside.

At Franklin Square, Jonathan Hansen, chair of emergency medicine, was having similar conversations with his staff.

"Because of the potential for exposure, we didn't want to necessarily bring patients in through the normal emergency entrances and expose other patients," he said.

Hansen said he and his staff were bracing for large numbers of casualties and awaiting the call to begin assembling a decontamination station in the hospital's outdoor ambulance bay when they got word there were few injuries.

The news surprised them, Hansen said.

"We feel like it's very fortunate and are amazed, really, that we didn't see more patients. With the extent of the explosion and the building collapses, we thought we would see a lot more," he said. "It was a good drill for our processes, but thankfully not more were injured."

Marshall said when Bayview got word of the derailment, longtime staff members immediately began talking about the collision in 1987 between a Conrail freight train and an Amtrak passenger train in Chase, in which 16 people were killed and more than 170 hurt. Hospital staff remembered treating many of the injured.

"That was the one that everyone kept referencing," Marshall said.

When they heard that casualties were minimal in Rosedale, Marshall said, Bayview staff let out "a collective exhale of relief."